ANNOTATIONS AND ADDITIONS. Ill 



the coast of Chili near Valdivia and Congeption, and thence streams 

 rapidly along the coast to the northward, as far as Cape Parina. On 

 the coast, near Lima, the temperature of the Pacific is 12. 5 Reau- 

 mur (60. 2 Fahr.), whilst in the same latitude out of the current it 

 is 21 R. (79.2 Fahr.) It is singular that so striking a fact should 

 have remained unnoticed until my visit to the shores of the Pacific, 

 in October 1802. 



The variations of temperature of different regions depend in a great 

 degree on the character of the bottom of the " aerial ocean," or on 

 the nature of the floor or base, whether land or sea, continental or 

 oceanic, on which the atmosphere rests. Seas, often traversed by 

 currents of warmer or colder water (oceanic rivers), have an effect 

 very different from that of continental masses, whether unbroken or 

 articulated, or of islands, which latter may be regarded as shallows 

 in the aerial ocean, and which, notwithstanding their small dimen- 

 sions, exert, often to a great distance, a notable influence on the 

 climate of the sea. In continental masses we must distinguish be- 

 tween sandy deserts devoid of vegetation, savannahs or grassy plains, 

 and forest-covered districts. In Upper Egypt and in South America, 

 Nouet in the former, and myself in the latter, found respectively at 

 noon the temperature of the ground composed of granitic sand 54. 2 

 and 48. 4 Reaumur (154 and 141 Fahr.). Many careful observa- 

 tions in Paris have given, according to Arago, 40 and 42 Reaumur, 

 122 and 126.5 Fahrenheit. (Asie Centrale, t. iii. p. 176.) The 

 Savannahs, which between the Missouri and the Mississippi are called 

 Prairies, and which appear in South America as the Llanos of Vene- 

 zuela and the Pampas of Buenos Ayres, are covered with small 

 monocotyledonous plants of the family of Cyperaceae, and with grasses 

 of which the thin pointed stalks or ears, and the delicate lanceolate 

 leaves or blades, radiate towards the unclouded sky, and possess an 

 extraordinary power of "emission." Wells and Daniell (Meteor. 

 Essays, 1827, p. 230 and 278) have even seen in our latitude, where 

 the atmosphere has so much less transparency, the thermometer sink 

 6. 5 or 8 of Reaumur (14. 5 or 18 Fahrenheit), on being placed 

 on the grass. Melloni, in a memoir, " Sull abassamento di tempera- 

 tura durante le notti placide e serene," 1847, pp. 47 and 53, has 

 shown how in a calm state of the atmosphere, which is a necessary 



